Calcium chloride and alkali metal salts, such as sodium chloride, are extensively used in very large quantities on the roads of many countries for snow and ice removal. The use of calcium chloride or sodium chloride has, however, met with some resistance due to their corrosive effect on ferrous metal and deleterious effect on concrete. Aqueous solutions of NaCl are known to oxidatively corrode ferrous metal and cause scaling or surface damage to concrete. Indeed, data has been released suggesting that the cost of the damage associated with the widespread application of salt is approximately fourteen times the direct cost associated with the application of the salt; D. M. Murray, et al., An Economic Analysis of the Environmental Impact of Highway Deicing, U.S. Environmental Protection Agency, Cincinnati, Ohio, EPA-600/A-76-105 (May 1976). Accordingly, it would be highly desirable to provide a deicing composition which deices rapidly, has a reduced level of concrete damage, and reduces corrosion of ferrous metallic objects.
Various additives have been proposed for mixing with salt to aid in inhibiting corrosion caused by the salt. British Patent No. 1328509 to Bishop et al. describes a composition suitable for use in the inhibition of corrosion caused by salt, which includes a water-soluble polyphosphate and a surface active agent. The surface active agent is various amine compounds. In an article by E. E. Steed, Road Research Laboratory, Ministry of Transport, Report LR268-1969, polymetaphosphate inhibitors which require the presence of calcium ions are described to be effective as a corrosion inhibitor for brine solutions.
There is a serious need to provide a low cost deicing composition which reduces corrosion such as oxidative corrosion caused by aqueous solutions of deicer salts. Depending on cost, a deicing composition which reduces such corrosion or rust would be highly desirable for use on roadways where large quantities of the deicing composition are required. The present invention is directed to providing a liquid deicing composition which is suitable for highway and sidewalk use and which resists corrosion of ferrous metal.
Accordingly, one of the principle objects of the invention is to provide a liquid deicing composition which deices rapidly. Another object of this invention is to provide a liquid deicing composition which causes a reduced level of corrosion to ferrous metal. Still another object of this invention is to provide a deicing composition which limits the deleterious effects of deicing on concrete which are normally associated with deicing salts such as NaCl. Yet another important object of this invention is to provide a method for making a deicing composition by using bittern.
The term "bittern" refers to the mother liquor remaining after the evaporation such as by solar evaporation of seawater to produce sodium chloride. Seawater and brines from inland lakes have been evaporated in ponds by the heat of the sun since earliest times. Intake or tide ponds are flooded with seawater at high tide. Brine is transferred by pumping or gravity to a series of concentrating ponds and finally to the crystallizing ponds from which the salt harvesting is done by machinery which scrapes the salt from the crystallizing beds. Some of the bittern remaining after the crystallization of salt is used for the production of bromine and compounds of magnesium. However, most of the bittern is a waste by-product for which there is no use. Hence, an important aspect and object of this invention is to provide a new use for a heretofore useless waste by-product.
These and other objects of the invention will become apparent from the following description.